It is good practice to arrange the burners in rows and to adjust the heating rate by control of the pressure of the combustion air for each row's piping manifold. The rate at which combustion air flows to each burner depends on the substantially constant flow resistance presented by the supply conduits and the restrictions incorporated therein. A separate pressure controller, referred to as a zero regulator, is associated with each burner to ensure the same pressure of the gaseous or vaporous fuel as the pressurized air. Downstream of each zero regulator manually adjustable throttle valve is provided in the fuel gas conduit effecting the adjustment of the fuel-air ratio.
Said shaft furnaces as well as the method of adjusting the heating rate have found widespread use and have been adapted to various additional conditions, such as fuel composition, charge analysis, and metallurgical process needs (German Pat. Specification No. 1,301,583, Printed German Application NO. 2,062,144).
Multiple technical conditions must be coordinated and suitably adjusted to obtain satisfactory results in the economical and metallurgical aims when operating such furnaces.
In the operation of furnaces of this kind it has been found to be particularly difficult to achieve all design- an operating conditions without adverse interdependence.